Safety control apparatus for gaseous fuel burners



S. G. ESKIN April 9, 1946.

SAFETY CONTROL APPARATUS FOR GASEOUS FUEL BURNERS Filed July 10, 1941 2 Sheets-Sheet l INVENTQR. cSAMuL-L 6. -$KIN.

WW ATTORNEY.

April 9, 1946. s. G. ESKIN ,3 ,2

SAFETY CONTROL APPARATUS FOR GASEOUS FUEL BURNERS Filed July 10, 1941 2 Sheets-Sheet 2 I FLAME GNITION 32 44 45 g 5; 2:22: 5 f I I uonmunr i0 azz-zam 46 SOLENOID 60\ awn-1y Qfiv:

i Lvvwfi J0 24- J5 J6v 4-8 I v ssZi1Evs 54 64 2 46 IGNITION NORMAL Q 62 CLOSED THERMAL INVENT OR. LSAMUEL G. EJK/N.

ATTORNEY.

Patented Apr. 9, 1946 SAFETY CONTROL APPARATUS FOR GASEOUS FUEL BURNERS Samuel G. Eskin, Pittsburgh, Pa., assignor to Robertshaw Thermostat Company, Youngwood, Pa., a corporation of'lennsylvania Application July 10, 1941, Serial No. 401,758

12 Claims.

This invention relates to Safety control apparatus for gaseous fuel burners and, more particularly, to heat-responsive'controls therefor.

In various gas appliances, including domestic gas ranges, it is customary to have a pilot burner from which the main burner is ignited. The fuel supplied to the main burner is controlled by a main fuel valve which may be either manually or thermostatically adjusted to vary the quantity of fuel' flowing to the main burner. Safety devices are used to prevent the escape of unburned fuel when the valve in the fuel supply line is opened when the pilot burner is not ignited.

The presence of a flame at the pilot burner has been utilized in various ways to control the operation of the main fuel valve and it is an object of this invention to prevent the flow of fuel to the main burner when the pilot burner fails to light.

Another object of the invention is to obtain rapid response to extinguishment of the pilot flame and equally rapid response to its presence.

Another object of the invention is to eliminate as far as possible all moving parts such as contacts, switches and the like which introduce inertia and tend to get out of order and interfere with dependable operation.

Another object of the invention is to maintain the thermally-sensitive device in operation overlong periods of time without deterioration or lack of its original sensitivity.

Another object of the invention is to construct the device of a simple, compact-and rugged design which will render it inexpensive to manufacture and reliable in operation.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view of a safety control apparatus constructed in accordance with this invention;

Fig. 2 is a wiring diagram of the electrical circuit shown in Fig. l; and

Fig. 3 is a wiring diagram of a modified form of the circuit.

Referring more particularly to the drawings, an oven compartment III of a gas range is shown as having ,the usual gas burner l2 supported therein. In this instance, the flow of gas to the burner I2 is under control of a thermostatic regulator H which is interposed between the gas inlet l6 and the burner l2. The regulator l4 also embodies a main gas cock (not shown) havin 20 and by means of which the inlet l6 may be opened and, closed in the usualmanner. The thermostatic control of the oven I0 is completed by the provision of the thermal-element 22 supported in the oven and operatively connected to the regulator l4. As such controls are well known and form no part of the present invention, further description is deemed unnecessary. A solenoid gas valve 24 of any known type i interposed in the gas inlet line, preferably between the regulator 14 and the burner 12. Such valves may be arranged, as in this instance, to be opened by energization of the solenoid and closed by gravity, as is well known. A wire 26 connects the solenoid gas valve 24 to one terminal of a main switch 28, shown as supported by the regulator l4 adjacent the gas cook stem l8. Operation of the main switch 28 may be effected by a cam 30 carried on the stem l8 and arranged to close the switch when the gas cock is rotated to open position. It will be understood that the thermostatic control may be omitted, leaving the main switch operable upon rotation of the gas cook, or separately operated if desired. The other terminal of the main switch 28 is connected by a wire 3| with the secondary of a transformer 32, the primary of which is connected to the power line.

A bracket 34 is secured to the main burner l2 and forms a support for a pilot flame burner 36 of any suitable type. The pilot flame burner 36 is located within the oven compartment I0 and is supplied through conduit 38 with fuel from the inlet l6 upon initial movement of the dial 2!! toward open position.

In order that any flow of gas to the pilot flame burner will be followed by its immediate ignition at that point without attention on the part of the operator, there is provided automatic means for igniting the pilot burner 36. This ignition means is electrical and takes the form of an ignition coil 40 positioned within the oven compartment and adjacent the pilot flame burner 36. One end of the ignition coil 40 is connected by a wire 42 with the solenoid gas valve 24. The other end of the ignition coil 40, in the embodiment shown in Figs. 1 and 2, is connected by a wire 45 tothe movable contact of an adjustable resistance element 44. The terminal of the adjustable resistance element 44 is connected by a wire 46 to the secondary 32 of the transformer.--

Referring further to the electrical circuit arrangement shown in Figs. 1 and 2, a second adjustable resistance element 48 is connected in a rotatable operating stem I8 carrying the dial 66 parallel circuit relationship with the first resistance element 44 by having its fixed terminal connected with the wire 46 and its movable contact connected by a wire 50 with the wire 42. As the wire 42 is connected with the ignition coil 40 the resistance element 44 is thus in series circuit with the ignition coil 40 and the resistance element 48 is in parallel circuit with both coil 40 and resistance 44. The resistance elements 44 and 48 may be adjusted to regulate the current flow to the ignition coil 40, the solenoid valve 24 and also to a resistor member 52.

The resistor member 52 is positioned in the path of the flame from the pilot burner 36 and is capable of changing its resistance with changes in temperature. Such a resistor may be in the form of a coil of wire formed from material having normally a relatively low resistance and a positive temperature coefficient of resistance. Such elements are known as ballast resistors. but it will be apparent that other types of flamesensitive devices or thermal resistance elements having the required characteristics may be substituted. In utilizing a ballast resistor for the purpose of this invention it is necessary that the current flowing thereto does not cause it to become sufliciently heated to operate the solenoid gas valve 24 in the absence of a flame at the pilot burner 38. The selection of a suitable coil is therefore dependent upon the voltage to be used in the system and will be apparent to those skilled in the art.

The resistor member 52 is arranged in parallel circuit with the solenoid valve and is connected at one end to th wire 42 and at the other end to a wire 54 which is connected to the wire 26. A normally closed thermal switch 56 is arranged in series circuit with the solenoid valve and comprises a heating coil 58 connected at one end to the solenoid valve and at the other end to a bimetallic arm 80 of the switch. The bimetallic arm is adapted to warp when the coil 58 is heated and become disengaged from a stationary contact 82 to which the wire 54 is connected. It is apparent that the circuit of the ignition coil 40, resistance elements 44 and 48 is arranged in series with the circuit of the solenoid gas valve 24, resistor element 52 and thermal switch 58.

In the embodiment shown in Fig. 3, a single constant resistance element 64 takes the place of the two variable resistance elements 44 and 48 of the embodiments shown in Figs. 1 and 2. The constant resistance element 64 is in series circuit with the ignition coil 40 and the parallel circuit arrangement with the second resistance element has been eliminated. Otherwise, the circuit and the elements comprising the control system are precisely the same as those described in connection with the previous embodiment and further description thereof is deemed-unnecessary.

In the operation of the apparatus described the closing of the main switch 28 by operation of the dial 20 establishes a circuit through the ignition coil 40 which, in a very short period, reaches igniting temperature. Operation of the dial 20 to close the switch 28 also opens the main gas cock controlling the inlet l6 and permits gas to flow through the conduit 38 to the pilot flame burner 34. The resistor member 52 becomes somewhat heated at this time but, as previously explained, an insuflicient amount of current reaches the solenoid valve to energize it from its closed position. Hence, no gas can flow through the main conduit past the solenoid valve to the main burner. The gas flowing from the pilot flame burner 36 meanwhile is quickly ignited by the ignition. coil 40 and the flame therefrom heats the resistor member I2. As the temperature of the resistor member I2 increases, its

resistance increases rapidly due to its high .positive resistant coeflicient causing more current to flow. through the solenoid gas valve 24. When the current through the solenoid gas valve has reached a sufllciently high value, the valve is actuated to open position and permits gas to pass to the main burner I! where it is ignited by the flame from the pilot burner 24.

Due to the provision in the embodiment shown in Figs. 1 and 2 of the pair of adjustable resistances 44 and 42 careful balancing of the resistances of the other elements of the safety control is rendered unnecessary. For example, the ignition coil may operate satisfactorily on ten amperes of current while the solenoid gas valve may require only eight amperes of current for actuation to open position. Hence, the resistance element 44 can be adjusted to pass ten amperes of current through the wire 4i to the ignition coil while the resistance 44 can be ad-- iusted to pass seven amperes through the wire 50. The current flowing in wires 45 and II will combine in the wire 42 and seventeen amperes will then pass to the parallel circuit composed of the solenoid valve 24 and the resistor member 52 where initially the major portion of the current passes through the latter. Thus, when the 'resistor member 52 reaches a temperature where eight amperes of current are passing through the solenoid gas valve 24 this valv will be actuated to open position.

In the embodiment shown in Fig. 3 the use of the constant resistance element 64 renders it necessary that an initial balancing of the resistances of the other elements be conducted. Thus, in normal operation of the control, when the resistor member 52 becomes heated by the flame of the pilot burner, sufficient current will pass through the solenoid gas valve 24 to cause it to open.

It will be apparent that when the dial 20 is operated to permit gas to flow to the pilot flame burner 36 and this burner does not produce a flame, no fuel can flow to th main burner. Such interruption of normal operation would occur by reason of failure of the ignition coil to ignite the fuel at the pilot flame burner and only the pilot gas would escape. Should the flame at the pilot burner become extinguished for any reason after the main burner is operating, then the resistor member 52 would cool and its resistance would be decreased, allowing more current to flow from the wire 42 to the wire 54 without passing through the solenoid valve 24. Consequently, the solenoid valve will close and prevent flow of fuel to the main burner l2.

Provision has been made in this invention to protect the solenoid gas valve 24 from the effects of a full flow of current therethrough should the resistor member 52 become broken or otherwise disconnected from the circuit. Such protection is provided by the normally closed thermal switch 56 which will become heated when the current rating of the solenoid gas valve is exceeded, causing the bimetal arm 60 to warp and open the circuit. In addition, opening of the circuit in this manner will cause th solenoid gas valve to close and shut on the flow of fuel to the main burner l2.

I claim:

1. A safety control apparatus for gaseous fuel burners having main and pilot burners and mean for controlling the supply of fuel thereto, said apparatus comprising a normally closed solenoid valve preventing the supply of fuel from passing to the main burner from said controlling means, an ignition coil in operative relation with the pilot burner and energized by operation of said controlling means, means for regulating the current to said ignition coil, and a thermal resistance element electrically connected in shunt with the solenoid valve and exposed to a flame upon operation of the pilot burner for governing the operation of said valve.

2. A safety control apparatus for gaseous fuel burners having main and pilot burners and means for controlling the supply of fuel thereto, said apparatus comprising a normally closed solenoid valve preventing the supply of fuel from passing to the main burner from said controlling means, an electric energizing circuit for said solenoid valve, an electric ignition coil in series with said solenoid valve to be energized by operation of said controlling means and being located in operative relation to the pilot burner, a resistance element in series with said coil and valve for regulating the current to said coil, and a thermal resistance element having normally a relatively low resistance and a positive temperature coefficient of resistance electrically connected in parallel with said circuit across said solenoid valve and exposed to the flame of the pilot burner for governing the operation of said valve.

3. A safety control apparatus for gaseous fuel burners having main and pilot burners and means for controlling the supply of fuel thereto, said apparatus comprising a normally closed solenoid valve preventing the supply of fuel from passing to the main burner from said controlling means, an electric energizing circuit for aid solenoid valve, an electric ignition coil in series circuit with said solenoid valve circuit to be energized by operation of said controlling means and being located in operative relation to the pilot burner,

an adjustable resistance element in series circuit with said ignition coil for regulating the current thereto, an adjustable resistance element in parallel circuit with the first said resistance and said ignition coil, said elements combining to regulate the current to said solenoid valve, a thermal resistance element in parallel circuit with saidsolenoid valve and exposed to a flame upon operation of th pilot burner for governing the operation of said valve, and means for dee er-- gizing said solenoid valve upon failure of said parallel circuit for the thermal resistance element.

4. A safety control apparatus for gas ranges comprising in combination, a main burner in the oven compartment of said range, a pilot burner in said oven compartment and adapted to light said main burner, a solenoid gas valve for controlling the flow of gas to said main burner, an electric energizing circuit for said solenoid valve, an electric ignition coil energized independently of said solenoid valve and disposed in operative relation with said pilot burner, a resistor located outside the oven compartment and adapted to limit-the current flow to said ignition coil, and a thermal resistance element electrically connected to, the solenoid valve and responsive to operation of the pilot burner for governing the operation of said valve, said element varying the amount of energizing current to the solenoid'valve in accordance with variations in temperature.

5. A-safety control apparatus for fuel burners and absence of said heat for rendering said current value insufficient when the fuel is not buming. a t 6. A safety control apparatus for fuel burners having main and pilot burners comprising a control device movable between fuel flow permitting and preventing positions to control the supply of fuel to the main burner, electromagnetic means for maintaining said device in a fuel flow permitting position, a source of current supply to saidv means having a value suflicient for said maintaining action, and a thermal resistance element electrically connected in shunt with said means and located to be heated by the pilot burner flame, said element varying in resistance between high and low values respectively in the presence and absence of said flame, said low value of resistance rendering the current value to said means insuflicient for the purpose aforesaid when the pilot burner does not produce a flame.

7. A safety control apparatus for fuel burners v having main and pilot burners and means for supplying fuel thereto, comprising a valve member movable between open and closed positions to control the fuel supply to the main burner, electromagnetic means for operating said valve member from closed to open position, a source of current supply for energizing said means and causing operation of said valve member to said open position, and a thermal resistance element having normally a relatively low resistance and a positive temperature coeflicient of resistance electrically connected in shunt with said means, said element being responsive to the presence of a flame at the pilot burner for increasing its resistance and thereby rendering the value of the current to said means suflicient for said energizing thereof, said current value being reduced b the low resistance of said'element sufiiciently to prevent opening-of said valve member if the pilot burner does not produce a flame.

8. A safety control apparatus for fuel burners having main and pilot burners and means-for' supplying fuel thereto, comprising a valve member movable between a normally closed and an open position to control the supply of fuel to the main burner, electromagnetic means foroperating said valve member to open position and maintaining it open, an energizing circuit for said means, and a thermal resistance element having normally a relatively low resistance and a positive temperature coeflicient of resistance electrically connected in shunt with said means and exposed to the flame of the pilot burner, said element increasing its resistance when heated by said flame sufliciently to render the'current value to said means capable of causing said operating and maintaining actions, said current value being rendered insufllcient for either action by the low resistance of said element if the pilot burner does not produce a flame.

9. A safety control apparatus for fuel burners having main and pilot burners and means for supplying fuel theretm comprising a control device movable between fuel flow permitting and preventing positions for controlling supply of fuel to the main burner, electromagnetic means ror maintaining said device in a fuel flow permitting position, an electric igniter for said pilot burner connected in series circuit with said electromagnetic means, a source of current supply to said igniter and means and having a value sumcient for said maintaining action, and a thermal resistance element electrically connected in shunt with said means and located to be heated by the pilot burner, said element varying in resistance between high and low values respectively in the presence and absence of said flame for rendering said current value insumcient when the pilot burner does not produce a name.

10. In a safety control system for fuel burners, the combination of electrically operable means movable between fuel flow permitting and preventing positions for controlling a supply of fuel to be burned, and means for controlling the operation of said electrically operable means comprising an electric circuit therefor including a thermal resistance element located to be heated by the burning fuel, said element varying in resistance according to the presence or absence of said heat and being adapted for reducing the 'current value to said electrically operable means sui'nciently to cause movement thereof from said flow permitting to flow preventing position when fuel flow permitting and preventing positions for controlling the supply of fuel to the main burner, and means for controlling the operation of said electrically operable means comprising an electric circuit therefor including a thermal resistance element located to be heated by a time at the pilot burner, said element varying in resistance according to the presence or absence of said flame and causing movement of said electrically operable means to flow permitting position in the presence of said flame, said element being adapted for reducing the current value to said electrically operable means sufllciently to cause movement thereof from said flow permitting to flow preventing position upon extinguishment of said flame.

12. A safety control apparatus for fuel burners having a source of electrical energy comprising an electromagnetic control device connected to receive energy from the source and movable between flow permitting and ilow preventing position for controlling a supply of fuel to be burned, and a thermal resistance element connected in shunt with said device for varying the energy supplied thereto according to whether the fuel is burning or not burning, said element being a coil of metal wire having normally a relatively low resistance and a positive temperature coeflicient of resistance located to be heated by the burning fuel and having sufficient resistance value when the fuel is not burning for reducing said energy supply and causing movement of said device from fuel flow permitting to fuel flow preventing position.

SAMUEL G. ESKIN. 

